40247-40-3Relevant articles and documents
Base-catalyzed aryl halide isomerization enables the 4-selective substitution of 3-bromopyridines
Bandar, Jeffrey S.,Puleo, Thomas R.
, p. 10517 - 10522 (2020/10/18)
The base-catalyzed isomerization of simple aryl halides is presented and utilized to achieve the 4-selective etherification, hydroxylation and amination of 3-bromopyridines. Mechanistic studies support isomerization of 3-bromopyridines to 4-bromopyridines proceedsviapyridyne intermediates and that 4-substitution selectivity is driven by a facile aromatic substitution reaction. Useful features of a tandem aryl halide isomerization/selective interception approach to aromatic functionalization are demonstrated. Example benefits include the use of readily available and stable 3-bromopyridines in place of less available and stable 4-halogenated congeners and the ability to converge mixtures of 3- and 5-bromopyridines to a single 4-substituted product.
Rh(I)-catalyzed ring-opening of hetaryne-furan diels-alder adducts: Rapid access to stereochemically defined heterocyclic scaffolds
Nguyen, Trung D.,Webster, Robert,Lautens, Mark
supporting information; experimental part, p. 1370 - 1373 (2011/05/15)
Probing the nucleophilic ring-opening of various bicyclic [2.2.1] hetaryne-furan Diels-Alder adducts revealed that efficient reactivity could be observed with heteroatom nucleophiles by using a cationic Rh(I) complex in combination with a chiral Josiphos-
Preparation of functionalized 3,4-pyridynes via 2-magnesiated diaryl sulfonates
Lin, Wenwei,Chen, Ling,Knochel, Paul
, p. 2787 - 2797 (2007/10/03)
The preparation of functionalized 3,4-pyridynes of type 1 as highly reactive intermediates has been achieved by the controlled elimination of readily generated 2-magnesiated diaryl sulfonates of type 2 obtained by a low temperature I/Mg- or Br/Mg-exchange starting from the corresponding halides of type 3. After trapping with furan, moderate to good yields of the desired functionalized cycloadducts of type 4 are obtained. The addition of a magnesium arylthiolate or magnesium phenylselenide to 3,4-pyridyne followed by quenching with an electrophile is also described.
Substituted 3,4-pyridynes: Clean cycloadditions
Connon, Stephen J.,Hegarty, Anthony F.
, p. 1245 - 1249 (2007/10/03)
The stabilisation of 3,4-pyridyne (1) by an alkoxy group adjacent to the ring nitrogen is reported. The regioselective lithiation of 2-ethoxy- (14), 2-methoxy- (18), 2-isopropoxy- (19) and 6-isopropoxy- (26) -3-chloropyridines with tertbutyllithium at low temperatures, followed by elimination of lithium chloride affords 2- and 6-alkoxy-3,4-pyridynes. These species are trapped m situ with furan in a Diels-Alder reaction to give 5-8 in 66-89% yield, and do not give products typical of polymerisation or nucleophilic addition to the 3,4-pyridyne intermediates. As a comparison treatment of 3-chloropyridine with furan and LDA gives only 19% of adduct (4). We also report the novel use of the isopropoxy (rather than methoxy) group in these systems, which can act as a heteroatomic electron donating group which inhibits a-lithiation by tert-butyllithium because of its increased steric bulk. The Royal Society of Chemistry 2000.
REGIOSELECTIVE ORTHO-LITHIATION OF HALOPYRIDINES. SYNTHESES OF ORTHO-DISUBSTITUTED PYRIDINES AND A CONVENIENT GENERATION OF 3,4-PYRIDYNE
Gribble, Gordon W.,Saulnier, Mark G.
, p. 151 - 169 (2007/10/02)
The regioselective ortho-lithiation of 3-chloro- (4), 3-fluoro- (7), 3-bromo- (10), 2-chloro- (22), and 4-chloropyridine (25) with lithium diisopropylamide affords, after quenching with various electrophiles, the corresponding ortho-disubstituted pyridine
SYNTHETIC CONNECTIONS TO THE DIRECTED ortho METALATION REACTION. 3,4-PYRIDINES FROM 4-TRIALKYLSILYL-3-PYRIDYL TRIFLATES
Tsukazaki, Masao,Snieckus, Victor
, p. 533 - 536 (2007/10/02)
4-Trialkylsilyl-3-pyridyl triflates (11a-b), derived from 9 and 12 by directed ortho metalation chemistry, serve as useful precursors of 3,4-pyridines (6a-b) and lead by cycloaddition and nucleophilic trapping reactions to products (13a-b, 14a-b, 15, 16a-b, and 17a-b).
Preparation of Didehydropyridines from (Trimethylsilyl)pyridines
Effenberger, Franz,Daub, Wolfgang
, p. 2119 - 2125 (2007/10/02)
Halogen-substituted (trimethylsilyl)pyridines 2, 3, 5-7 and trifluoromethylsulfonyloxy-substituted (trimethylsilyl)pyridines 9b, 11b are obtained from 2- and 3-halopyridines 1, 4 or hydroxypyridines 8, 10, and 12.Reactions of the 3- and 2-(trimethylsilyl)pyridines 2, 9b and 11b with bases in the presence of furans 15 give only protodesilylation or hydrolysis products but no indication is found for the formation of a 2,3-didehydropyridine. 3-Bromo-4-(trimethylsilyl)pyridine (5a) reacts with KOCMe3 in the presence of furan (15a) to give a mixture of products from which the isoquinoline derivative 20 and the tert-butoxypyridines 23, 24 are formed by addition to 3,4-didehydropyridine.Under comparable conditions far higher yields of 3,4-didehydropyridines are obtained by treatment of the 3-halo-2,4-bis(trimethylsilyl)pyridines 7 with strong bases. Key Words: Didehydropyridines, synthesis of
Synthesis of Cycloproparenes via Aromatization of 7-Oxanorbornenes with Low-Valent Titanium
Mueller, Paul,Schaller, Jean-Pierre
, p. 1608 - 1617 (2007/10/02)
1H-Cyclopropanaphthalene 3c and the 2,7-diphenyl-substituted derivative 3a have been synthesized via cycloaddition of the appropriate isobenzofurans 1a and 1b to 1-bromo-2-chlorocyclopropene and aromatization of the adducts with low-valent Ti.The same procedure afforded the 2,7-dimethyl-1H-cyclopropaisoquinoline (15), but failed for the parent azacompound.Reaction of adducts of furans to 1-bromo-2-chlorocyclopropenes with low-valent Ti produced mixtures of cyclopropabenzenes 19 and 1,6-dihalogeno-1,3,5-cycloheptatrienes 18.The latter could be converted to cyclopropabenzenes with BuLi.
A NEW PRECURSOR TO 3,4-DIDEHYDROPYRIDINE, AND ITS USE IN THE SYNTHESIS OF THE ANTITUMOR ALKALOID ELLIPTICINE
May, Christopher,Moody, Christopher J.
, p. 247 - 250 (2007/10/02)
A concise synthesis of the antitumor alkaloid ellipticine (1) is reported.The route involves a Diels-Alder reaction between 1,4-dimethylpyranoindol-3-one (3), easily prepared in two steps from indole, and 3,4-didehydropyridine (4), and for its successful execution required the development of a new thermal, reagent-free precursor to the aryne.This precursor, 3-(3,3-dimethyltriazen-1-yl)pyridine-4-carboxylic acid (10a), prepared from 3-aminopyridine-4-carboxylic acid, decomposes in boiling acetonitrile to generate 3,4-didehydropyridine which can be intercepted in Diels-Alder reactions with tetraphenylcyclopentadienone, furan, and 2,5-dimethylfuran.The triazenes (10b) and (10c) can be prepared and decomposed similarly.The key Diels-Alder reaction between the pyranoindolone (3) and 3,4-didehydropyridine (4) gives ellipticine (1) in 20 percent yield, together with an equal amount of isoellipticine (14).
Directed Lithiation of 4-Halopyridines: Chemoselectivity, Regioselectivity and Application to Synthesis
Marsais, F.,Trecourt, F.,Breant, P.,Queguiner, G.
, p. 81 - 87 (2007/10/02)
4-Chloro and 4-fluoropyridines were ortho-lithiated by n-butyllithium-TMEDA chelate or lithium diisopropylamide at low temperature.The resulting 3-lithio 4-halopyridines were reacted with electrophiles which led to various 3,4-disubstituted pyridines.The versatility of this functionalization is enhanced by the 4-halogen reactivity towards nucleophiles such as water, methylate and amines.Some of the 3,4-disubstituted synthons were annelated to naphthyridine, xanthone and coumarin or condensed to Hantzsch-ester or to "chlotrimazol" analogues.Lithiation of 4-fluoropyridine led in one step to 3,4-pyridyne, which was trapped by cycloaddition with furans.
